Integrated chip with inter-wire cavities

ABSTRACT

The present disclosure relates to an integrated chip comprising a substrate. A first conductive wire is over the substrate. A second conductive wire is over the substrate and is adjacent to the first conductive wire. A first dielectric cap is laterally between the first conductive wire and the second conductive wire. The first dielectric cap laterally separates the first conductive wire from the second conductive wire. The first dielectric cap includes a first dielectric material. A first cavity is directly below the first dielectric cap and is laterally between the first conductive wire and the second conductive wire. The first cavity is defined by one or more surfaces of the first dielectric cap.

BACKGROUND

Modern day integrated chips contain millions of semiconductor devices.The semiconductor devices are electrically interconnected by way ofback-end-of-the-line (BEOL) metal interconnect layers that are formedabove the devices. A typical integrated chip comprises a plurality ofBEOL metal interconnect layers including different sized metal wiresvertically coupled together with metal vias.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1A illustrates a cross-sectional view of some embodiments of anintegrated chip comprising a first metal wire and a second metal wirethat are laterally separated by a first cavity.

FIG. 1B illustrates a top view of some embodiments of the integratedchip of FIG. 1A.

FIG. 2 illustrates a cross-sectional view of some alternativeembodiments of the integrated chip of FIG. 1A in which a firstdielectric cap over the first cavity has a curved lower surface.

FIG. 3 illustrates a cross-sectional view of some alternativeembodiments of the integrated chip of FIG. 1A in which the first cavityis defined by one or more surfaces of a first residual sacrificialstructure.

FIG. 4 illustrates a cross-sectional view of some alternativeembodiments of the integrated chip of FIG. 1A in which the first cavityis defined by a first dielectric cap and a residual dielectricstructure.

FIG. 5 illustrates a cross-sectional view of some alternativeembodiments of the integrated chip of FIG. 1A in which a first residualcapping structure is over the first metal wire and a second residualcapping structure is over the second metal wire.

FIG. 6A illustrates a cross-sectional view of some alternativeembodiments of the integrated chip of FIG. 1A in which a firstdielectric cap surrounds the first cavity.

FIG. 6B illustrates a cross-sectional view of some alternativeembodiments of the integrated chip of FIG. 6A in which the first cavityhas a different size and/or shape than a second cavity.

FIG. 6C illustrates a cross-sectional view of some alternativeembodiments of the integrated chip of FIG. 6A in which a first residualcapping structure is over the first metal wire and a second residualcapping structure is over the second metal wire.

FIGS. 7-22 illustrate cross-sectional views of some embodiments of amethod for forming an integrated chip comprising a first metal wire anda second metal wire that are laterally separated by a first cavity.

FIG. 23 illustrates a flow diagram of some embodiments of a method forforming an integrated chip comprising a first metal wire and a secondmetal wire that are laterally separated by a first cavity.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Some integrated chips include one or more semiconductor devices along asubstrate and a plurality of metal wires over the substrate that may beelectrically connected to the one or more semiconductor devices. Theplurality of metal wires are laterally separated from one another by adielectric layer. The dielectric layer may, for example, comprisesilicon oxide, silicon nitride, or some other suitable dielectric.

A challenge with these integrated chips is that a capacitance thatexists between the plurality of metal wires contributes to aresistive-capacitive (RC) delay in the integrated chip. The capacitanceis proportional to a dielectric constant of the dielectric layer thatseparates the metal wires. Thus, metal wires that are separated by amaterial having a high dielectric constant (e.g., about 3.9 for siliconoxide) may exhibit a high capacitance and hence a high RC delay. As aresult, a performance of the integrated chip may be low.

Various embodiments of the present disclosure are related to anintegrated chip comprising one or more cavities for improving aperformance of the integrate chip, and a method of forming theintegrated chip for improving a reliability of the integrated chip. Forexample, an integrated chip comprises an etch-stop layer over asubstrate. A first metal wire and a second metal wire are over theetch-stop layer and the second metal wire is laterally adjacent to thefirst metal wire. The etch-stop layer laterally separates the firstmetal wire from the second metal wire. A first dielectric cap isdirectly over the etch-stop layer and laterally between the first metalwire and the second metal wire. A first cavity is directly below thefirst dielectric cap and directly over the etch-stop layer. The firstcavity laterally separates the first metal wire from the second metalwire. Further, the first cavity comprises a first gas and the firstcavity is defined by one or more surfaces of the first dielectric cap.

The first gas may, for example, comprise air or some other suitablegas(es) and hence may have a low dielectric constant (e.g., about 1 forair). Thus, by including the first cavity in the integrated chip betweenthe first and second metal wires, a dielectric constant between thefirst and second metal wires may be low. As a result, a capacitancebetween the first and second metal wires may also be low and hence an RCdelay of the integrated chip may be reduced. Thus, a performance of theintegrated chip may be improved.

Further, a method for forming the first cavity may prevent causingdamage to the first metal wire and the second metal wire throughout themethod. In various embodiments, the method comprises forming a firstcapping structure over the first metal wire and a second cappingstructure over the second metal wire before removing a first dielectricstructure from between the first and second metal wires with an etch.The first and second capping structures may protect the underlying firstand second metal wires from being damaged by the etch. Thus, the firstand second metal wires may be undamaged after forming the first cavity.For example, sidewalls and top surfaces of the first and second metalwire may be substantially planar and/or devoid of nanoscopic voids afterthe first cavity is formed. As a result, a structural integrity of thefirst and second metal wires may be maintained and hence a reliabilityof the first and second metal wires may be high.

Referring to FIGS. 1A and 1B simultaneously, FIG. 1A illustrates across-sectional view 100 of some embodiments of an integrated chipcomprising a first metal wire 110 a and a second metal wire 110 b thatare laterally separated by a first cavity 114 a, while FIG. 1Billustrates a top view 150 of some embodiments of the integrated chip ofFIG. 1A. The cross-sectional view 100 of FIG. 1A may, for example, betaken across line A-A′ of FIG. 1B.

In such embodiments, the integrated chip comprises a plurality ofsemiconductor devices 104 along a substrate 102. A first interconnectstructure 106 is over the substrate 102. Further, a first etch-stoplayer 108 extends over the first interconnect structure 106.Furthermore, a plurality of metal wires 110, a plurality of dielectriccaps 112, and a plurality of cavities 114 extend over the firstinterconnect structure 106.

For example, the first metal wire 110 a and the second metal wire 110 bof the plurality of metal wires 110 extend over the first interconnectstructure 106. The first metal wire 110 a is laterally adjacent to thesecond metal wire 110 b. A first dielectric cap 112 a of the pluralityof dielectric caps 112 is directly over the first etch-stop layer 108and is laterally between the first metal wire 110 a and the second metalwire 110 b. The first dielectric cap 112 a laterally separates the firstmetal wire 110 a from the second metal wire 110 b along tops of thefirst and second metal wires 110 a, 110 b. In addition, the firstetch-stop layer 108 laterally separates the first metal wire 110 a fromthe second metal wire 110 b along bottoms of the first and second metalwires 110 a, 110 b.

In some embodiments, top surfaces of the plurality of metal wires 110are substantially planar (e.g., the first and second top surfaces maynot deviate from their respective planes by more than about 1 nanometer,more than about 5 nanometers, more than about 10 nanometers, or someother suitable value). For example, in some embodiments, a first topsurface of the first metal wire 110 a and a second top surface of thesecond metal wire 110 b are substantially planar. Further, in someembodiments, sidewalls of the plurality of metal wires 110 are alsosubstantially planar. For example, in some embodiments, a first sidewallof the first metal wire 110 a and a second sidewall of the second metalwire 110 b that faces the first sidewall are substantially planar.

In some embodiments, sidewalls and top surfaces of the first metal wire110 a and the second metal wire 110 b are devoid of nanoscopic voids(e.g., nanoscopic defects). For example, in such embodiments, thesidewalls and the top surfaces of the first metal wire 110 a and thesecond metal wire 110 b are devoid of voids and/or defects that aregreater than about 5 angstroms in width, greater than about 1 nanometerin width, greater than about 5 nanometers in width, or some othersuitable value.

In some embodiments, the first and second metal wires 110 a, 110 b havefirst and second theoretical sheet resistances, respectively, and havefirst and second measured sheet resistances, respectively. In suchembodiments, the first measured sheet resistance may differ from thefirst theoretical sheet resistance by less than 1 percent, less than 5percent, less than 10 percent, less than 20 percent, less than 30percent, or some other suitable value. Likewise, the second measuredsheet resistance may differ from the second theoretical sheet resistanceby less than 1 percent, less than 5 percent, less than 10 percent, lessthan 20 percent, less than 30 percent, or some other suitable value.

In some embodiments, the first and second metal wires 110 a, 110 b mayhave any of the aforementioned characteristics (e.g., planar surfaces,surfaces devoid of nanoscopic voids, and/or small differences inmeasured and theoretical sheet resistances, etc.) because a method forforming the integrated chip may prevent causing damage to the firstmetal wire 110 a and the second metal wire 110 b throughout the method.

Further, the first cavity 114 a of the plurality of cavities 114 isdirectly below the first dielectric cap 112 a and is directly over thefirst etch-stop layer 108. The first cavity 114 a laterally separatesthe first metal wire 110 a from the second metal wire 110 b. The firstcavity 114 a is defined by one or more surfaces of the first dielectriccap 112 a and the first cavity 114 a comprises a first gas. In someembodiments, the first gas may, for example, be or comprise air, someother suitable gas having a low dielectric constant, or the like.

In some embodiments, the first cavity 114 a is defined by an uppersurface of the first etch-stop layer 108, a sidewall of the first metalwire 110 a, a sidewall of the second metal wire 110 b, and a lowersurface of the first dielectric cap 112 a. In some embodiments, thelower surface of the first dielectric cap 112 a defines a top of thefirst cavity 114 a. Further, the lower surface of the first dielectriccap 112 a is below a top surface of the first metal wire 110 a and belowa top surface of the second metal wire 110 b. In some embodiments, awidth of the first cavity 114 a is approximately equal to a distancebetween the first metal wire 110 a and the second metal wire 110 b.

By including the first cavity 114 a in the integrated chip between thefirst metal wire 110 a and the second metal wire 110 b, a dielectricconstant between the first and second metal wires 110 a, 110 b may below. As a result, a capacitance between the first and second metal wires110 a, 110 b may also be low and hence an RC delay of the integratedchip may be reduced. Thus, a performance of the integrated chip may beimproved.

In some embodiments, the integrated chip further comprises a secondinterconnect structure 116 over the plurality of metal wires 110.

Although the first interconnect structure 106 and the secondinterconnect structure 116 are illustrated generically in FIG. 1 , itwill be appreciated that the first interconnect structure 106 and thesecond interconnect structure 116 may each comprise one or more levelsof interconnect. For example, the first interconnect structure 106and/or the second interconnect structure 116 may comprise one or moreetch-stop layers, one or more dielectric layers, one or more metalwires, one or more metal vias, one or more contacts, some other suitableinterconnect features, or any combination of the foregoing.

In some embodiments, the substrate 102 may, for example, comprisesilicon, some III-V material, some other semiconductor material, or thelike.

In some embodiments, the plurality of semiconductor devices 104 may, forexample, be or comprise metal-oxide-semiconductor field-effecttransistors (MOSFETs), bipolar junction transistors (BJTs), junctionfield-effect transistors (JFETs), fin field-effect transistors(FinFETs), gate-all-around field-effect transistors (GAA FETs), someother suitable semiconductor device(s), or the like.

In some embodiments, the plurality of dielectric caps 112 may, forexample, comprise any of silicon oxide, silicon nitride, siliconoxynitride, silicon carbide, silicon oxycarbide, silicon carbonitride,silicon oxycarbonitride, some other low-k dielectric (e.g., having adielectric constant of less than about 3.9), some other extreme low-kdielectric (e.g., having a dielectric constant of less than about 2), orsome other suitable dielectric.

In some embodiments, the first etch-stop layer 108 may, for example,comprise any of silicon oxide, silicon nitride, silicon oxynitride,silicon carbide, silicon oxycarbide, silicon carbonitride, siliconoxycarbonitride, aluminum oxide, aluminum oxynitride, or some othersuitable dielectric.

In some embodiments, the plurality of metal wires 110 may, for example,comprise any of tantalum, tantalum nitride, titanium nitride, copper,cobalt, ruthenium, molybdenum, iridium, tungsten, some other conductivematerial, or some other suitable material.

FIG. 2 illustrates a cross-sectional view 200 of some alternativeembodiments of the integrated chip of FIG. 1A in which the firstdielectric cap 112 a over the first cavity 114 a has a curved lowersurface.

In such embodiments, the plurality of dielectric caps 112 have curved(e.g., convex) lower surfaces that define tops of the plurality ofcavities 114. For example, a bottom of the first dielectric cap 112 a isbelow a first point where the first dielectric cap 112 a meets the firstmetal wire 110 a and below a second point where the first dielectric cap112 a meets the second metal wire 110 b.

The plurality of dielectric caps 112 may have curved lower surfaces dueto a sacrificial layer (e.g., 1402 of FIG. 14 ) being recessed to form aplurality of sacrificial structures (e.g., 1502 of FIG. 15 ), where therecessing results in the plurality of sacrificial structures havingcurved upper surfaces (e.g., 1502 u of FIG. 15 ), and due to adielectric layer (e.g., 1602 of FIG. 16 ) being subsequently depositedover the plurality of sacrificial structures.

Further, in some embodiments, the first interconnect structure 106 may,for example, comprise a lower etch-stop layer 106 e, a lower dielectriclayer 106 d, and one or more contacts 106 c. In some embodiments, otherinterconnect levels and/or features may also be included.

Furthermore, in some embodiments, the second interconnect structure 116may, for example, comprise one or more upper etch-stop layers 116 e, oneor more upper dielectric layers 116 d, one or more upper vias 116 v, oneor more upper metal wires 116 w, one or more upper cavities 116 c, orsome other suitable features (e.g., bond pads, solder bumps, etc.). Forexample, in such embodiments, the one or more upper vias 116 v may beseparated by the upper cavities 116 c. Further, the one or more uppermetal wires 116 w may be over the one or more upper vias 116 v and alsomay be separated by the upper cavities 116 c. In some embodiments, otherinterconnect levels and/or features may also be included.

In some embodiments, any of the lower dielectric layer 106 d and the oneor more upper dielectric layers 116 d may, for example, comprise any ofsilicon oxide, silicon nitride, silicon oxynitride, silicon carbide,silicon oxycarbide, silicon carbonitride, silicon oxycarbonitride, someother low-k dielectric (e.g., having a dielectric constant of less thanabout 3.9), some other extreme low-k dielectric (e.g., having adielectric constant of less than about 2), or some other suitabledielectric.

In some embodiments, any of the lower etch-stop layer 106 e and the oneor more upper etch-stop layers 116 e may, for example, comprise any ofsilicon oxide, silicon nitride, silicon oxynitride, silicon carbide,silicon oxycarbide, silicon carbonitride, silicon oxycarbonitride,aluminum oxide, aluminum oxynitride, or some other suitable dielectric.

In some embodiments, the one or more contacts 106 c may, for example,comprise tungsten, copper, aluminum, titanium, tantalum, or some othersuitable material.

In some embodiments, any of the one or more upper vias 116 v and the oneor more upper metal wires 116 w may, for example, comprise any oftantalum, tantalum nitride, titanium nitride, copper, cobalt, ruthenium,molybdenum, iridium, tungsten, some other conductive material, or someother suitable material.

In some embodiments, the one or more upper cavities 116 c may, forexample, comprise air, nitrogen, oxygen, carbon dioxide, some othersuitable gas having a low dielectric constant, or any combination of theforegoing.

FIG. 3 illustrates a cross-sectional view 300 of some alternativeembodiments of the integrated chip of FIG. 1A in which the first cavity114 a is defined by one or more surfaces of a first residual sacrificialstructure 302 a.

In such embodiments, the plurality of cavities 114 are defined by one ormore surfaces of a plurality of residual sacrificial structures 302. Forexample, the first residual sacrificial structure 302 a of the pluralityof residual sacrificial structures 302 defines, at least in part, thefirst cavity 114 a of the plurality of cavities 114. The first residualsacrificial structure 302 a may, for example, be disposed on any of anupper surface of the first etch-stop layer 108, a sidewall of the firstmetal wire 110 a, a sidewall of the second metal wire 110 b, and a lowersurface of the first dielectric cap 112 a.

In some embodiments (not shown), the first residual sacrificialstructure 302 a is on all of the aforementioned surfaces such that thefirst cavity 114 a is enclosed by the first residual sacrificialstructure 302 a. In some other embodiments, the first residualsacrificial structure 302 a is only on some of the aforementionedsurfaces such that the first residual sacrificial structure 302 a onlypartially defines the first cavity 114 a. For example, the firstresidual sacrificial structure 302 a may be on the upper surface of thefirst etch-stop layer 108 and on sidewalls of the first and second metalwires 110 a, 110 b such that a bottom of the first cavity 114 a isdefined by an upper surface of the first residual sacrificial structure302 a while a top of the first cavity 114 a is defined by a lowersurface of the first dielectric cap 112 a.

The first residual sacrificial structure 302 a may be on any of theupper surface of the first etch-stop layer 108, the sidewall of thefirst metal wire 110 a, the sidewall of the second metal wire 110 b, andthe lower surface of the first dielectric cap 112 a because a firstsacrificial structure (e.g., 1502 a of FIGS. 15 and 17 ) may not beentirely removed from said surfaces during a sacrificial structureremoval process (see, for example, FIGS. 16 and 17 ).

In some embodiments, the plurality of residual sacrificial structures302 may, for example, comprise some organic material (e.g., somecarbon-based material) or some other suitable material.

Further, in some embodiments, the first interconnect structure 106 may,for example, comprise middle-of-line (MOL) interconnect. For example,the MOL interconnect may comprise one or more lower etch-stop layers 106e, one or more lower dielectric layer 106 d, one or more contacts 106 c,one or more lower metal wires 106 w, one or more lower vias 106 v, orsome other suitable features.

FIG. 4 illustrates a cross-sectional view 400 of some alternativeembodiments of the integrated chip of FIG. 1A in which the first cavity114 a is defined by the first dielectric cap 112 a and a residualdielectric structure 402.

In such embodiments, a first sidewall of the residual dielectricstructure 402 extends along a sidewall of the second metal wire 110 b,and a second sidewall of the residual dielectric structure 402 oppositethe first sidewall partially defines the first cavity 114 a. Theresidual dielectric structure 402 also extends along a sidewall of thefirst dielectric cap 112 a and extends between the first dielectric cap112 a and the second metal wire 110 b. The residual dielectric structure402 may comprise a same or different material than the first dielectriccap 112 a. For example, the residual dielectric structure 402 maycomprise any of silicon oxide, silicon nitride, silicon oxynitride,silicon carbide, silicon oxycarbide, silicon carbonitride, siliconoxycarbonitride, some other low-k dielectric (e.g., having a dielectricconstant of less than about 3.9), some other extreme low-k dielectric(e.g., having a dielectric constant of less than about 2), or some othersuitable dielectric.

In some embodiments, the residual dielectric structure 402 may be on thesidewall of the second metal wire 110 b due to a misalignment or offsetwhen depositing and pattering a capping layer (e.g., 1202 of FIG. 12 )that acts as a hard mask (see, for example, FIG. 13 ). Thus, a portion(e.g., 1202 z of FIG. 12 ) of the capping layer may remain over aportion of a first dielectric structure (e.g., 904 a of FIG. 12 ) whenpatterning the first dielectric structure (e.g., 904 a of FIG. 12 ). Asa result, the residual dielectric structure 402 may not be removedduring the patterning (see, for example, FIGS. 12 and 13 ).

In some other embodiments, the residual dielectric structure 402 may beon the sidewall of the second metal wire 110 b due to a loss ofselectivity when forming the capping layer (e.g., 1202 of FIG. 12 ) on atop of the second metal wire 110 b (see, for example, FIG. 12 ). Thus, aportion (e.g., 1202 z of FIG. 12 ) of the capping layer may be formedover a first dielectric structure (e.g., 904 a of FIG. 12 ). In turn,the residual dielectric structure 402 may not be removed when patterningthe first dielectric structure (see, for example, FIGS. 12 and 13 ).

FIG. 5 illustrates a cross-sectional view 500 of some alternativeembodiments of the integrated chip of FIG. 1A in which a first residualcapping structure 502 a is over the first metal wire 110 a and a secondresidual capping structure 502 b is over the second metal wire 110 b.

In such embodiments, a plurality of residual capping structures 502 areon top surfaces of the plurality of metal wires 110. For example, thefirst residual capping structure 502 a is on a top surface of the firstmetal wire 110 a and the second residual capping structure 502 b is on atop surface of the second metal wire 110 b. Further, top surfaces of theplurality of residual capping structures 502 and top surfaces of theplurality of dielectric caps 112 may be approximately coplanar.Moreover, top surfaces of the plurality of dielectric caps 112 are abovetop surfaces of the plurality of metal wires 110.

In some embodiments, the plurality of residual capping structures 502may be on top surfaces of the plurality of metal wires 110 due to aplurality of capping structures (e.g., 1204 of FIGS. 12 to 17 ) notbeing entirely removed from the tops of the plurality of metal wires 110during a planarization process (see, for example, FIGS. 17 and 18 ).

In some embodiments, the plurality of residual capping structures 502may comprise one or more dielectrics or one or more metals. For example,the plurality of residual capping structures 502 may, for example,comprise any of hafnium oxide (e.g., HfO), lithium niobium oxide (e.g.,LiNbO), lithium nickel oxide (e.g., LiNiO), magnesium oxide (e.g., MgO),manganese oxide (e.g., MnO), molybdenum oxide (e.g., MoO), niobium oxide(e.g., NbO), nickel oxide (e.g., NiO), silicon oxide (e.g., SiO),silicon oxycarbide (e.g., SiOC), silicon oxycarbonitride (e.g., SiOCN),silicon oxynitride (e.g., SiON), silicon carbide (e.g., SiC), tin oxide(e.g., SnO), tin silicon oxide (e.g., SnSiO), strontium oxide (e.g.,SrO), tantalum oxide (e.g., TaO), tantalum oxynitride (e.g., TaON),titanium oxide (e.g., TiO), titanium oxynitride (e.g., TiON), tungstenoxide (e.g., WO), zinc oxide (e.g., ZnO), zirconium oxide (e.g., ZrOx),some other suitable dielectric, tantalum (e.g., Ta), tantalum nitride(e.g., TaN), titanium nitride (e.g., TiN), copper (e.g., Cu), cobalt(e.g., Co), ruthenium (e.g., Ru), molybdenum (e.g., Mo), iridium (e.g.,Ir), tungsten (e.g., W), or some other suitable metal.

FIG. 6A illustrates a cross-sectional view 600 of some alternativeembodiments of the integrated chip of FIG. 1A in which the firstdielectric cap 112 a surrounds the first cavity 114 a.

In such embodiments, the first dielectric cap 112 a is on a sidewall ofthe first metal wire 110 a, on a sidewall of the second metal wire 110b, on a lower surface of the second interconnect structure 116 (e.g., ona lower surface of the upper etch-stop layer 116 e of FIG. 2 ), and onan upper surface of the first etch-stop layer 108 such that the firstdielectric cap 112 a encloses the first cavity 114 a. In other words,the first dielectric cap 112 a extends in a closed path along a boundaryof the first cavity 114 a to surround the first cavity 114 a. In yetother words, the first cavity 114 a exists within the first dielectriccap 112 a and is defined by one or more inner surfaces of the firstdielectric cap 112 a.

The first dielectric cap 112 a may surround the first cavity 114 a dueto the conformality and/or a fill capability of the deposition processused to form the first dielectric cap 112 a, and due to a pitch betweenthe first metal wire 110 a and the second metal wire 110 b being small(e.g., less than 100 nanometers or some other suitable value).

In some embodiments, the second interconnect structure 116 may, forexample, comprise one or more upper etch-stop layers 116 e, one or moreupper dielectric layers 116 d, one or more upper vias 116 v, one or moreupper metal wires 116 w, one or more upper cavities 116 c, or some othersuitable features (e.g., bond pads, solder bumps, etc.). For example, insuch embodiments, the one or more upper vias 116 v may be separated bythe upper cavities 116 c. Further, the one or more upper metal wires 116w may be over the one or more upper vias 116 v and also may be separatedby the upper cavities 116 c. In some embodiments, other interconnectlevels and/or features may also be included.

FIG. 6B illustrates a cross-sectional view 610 of some alternativeembodiments of the integrated chip of FIG. 6A in which the first cavity114 a has a different size and/or shape than a second cavity 114 b.

In such embodiments, the second cavity 114 b is adjacent to the firstcavity 114 a and is separated from the first cavity by the second metalwire 110 b. Further, a width 114 aw of the first cavity 114 a is lessthan a width 114 bw of the second cavity 114 b. In addition, a height114 ah of the first cavity 114 a is less than a height 114 bh of thesecond cavity 114 b.

Further, in some embodiments, a second dielectric cap 112 b surroundsthe second cavity 114 b. In such embodiments, the first dielectric cap112 a may extend in a first closed path along a first boundary of thefirst cavity 114 a to surround the first cavity 114 a and the seconddielectric cap 112 b may extend in a second closed path, different fromthe first closed path, along a second boundary of the second cavity 114b to surround the second cavity 114 b. For example, the second closedpath may differ from the first closed path in length, shape, or thelike.

The first cavity 114 a may have a different size and/or shape than thesecond cavity 114 b due to difference in pitch between the plurality ofmetal wires 110. Alternatively, the difference in the size and/or shapeof the first and second cavities 114 a, 114 b may be a result of thedeposition process which forms the first dielectric cap 112 a and thesecond dielectric cap 112 b (e.g., the difference may occur naturallyduring the deposition process).

In addition, in some embodiments, a third dielectric cap 112 c isadjacent to the first dielectric cap 112 a and is separated from thefirst dielectric cap 112 a by the first metal wire 110 a. Further, athird metal wire 110 c is adjacent to the first metal wire 110 a and isseparated from the first metal wire 110 a by the third dielectric cap112 c. In some embodiments, a cavity may not exist within the thirddielectric cap 112 c. This may be because a pitch between the firstmetal wire 110 a and the third metal wire 110 c is substantially large(e.g., large enough that the material deposited between the first metalwire 110 a and the third metal wire 110 c to form the third dielectriccap 112 c fills a spacing between the first metal wire 110 a and thethird metal wire 110 c completely).

FIG. 6C illustrates a cross-sectional view 620 of some alternativeembodiments of the integrated chip of FIG. 6A in which a first residualcapping structure 602 a is over the first metal wire 110 a and a secondresidual capping structure 602 b is over the second metal wire 110 b.

In such embodiments, a plurality of residual capping structures 602 areon top surfaces of the plurality of metal wires 110. For example, thefirst residual capping structure 602 a is on a top surface of the firstmetal wire 110 a and the second residual capping structure 602 b is on atop surface of the second metal wire 110 b. Further, top surfaces of theplurality of residual capping structures 602 and top surfaces of theplurality of dielectric caps 112 may be approximately coplanar.Moreover, top surfaces of the plurality of dielectric caps 112 are abovetop surfaces of the plurality of metal wires 110.

In some embodiments, the plurality of residual capping structures 602may be on top surfaces of the plurality of metal wires 110 due to aplurality of capping structures (e.g., 1204 of FIGS. 12, 13, and 20 )not being entirely removed from the tops of the plurality of metal wires110 during a planarization process (see, for example, FIGS. 20 and 21 ).

In some embodiments, the plurality of residual capping structures 602may comprise one or more dielectrics or one or more metals. For example,the plurality of residual capping structures 602 may, for example,comprise any of hafnium oxide (e.g., HfO), lithium niobium oxide (e.g.,LiNbO), lithium nickel oxide (e.g., LiNiO), magnesium oxide (e.g., MgO),manganese oxide (e.g., MnO), molybdenum oxide (e.g., MoO), niobium oxide(e.g., NbO), nickel oxide (e.g., NiO), silicon oxide (e.g., SiO),silicon oxycarbide (e.g., SiOC), silicon oxycarbonitride (e.g., SiOCN),silicon oxynitride (e.g., SiON), silicon carbide (e.g., SiC), tin oxide(e.g., SnO), tin silicon oxide (e.g., SnSiO), strontium oxide (e.g.,SrO), tantalum oxide (e.g., TaO), tantalum oxynitride (e.g., TaON),titanium oxide (e.g., TiO), titanium oxynitride (e.g., TiON), tungstenoxide (e.g., WO), zinc oxide (e.g., ZnO), zirconium oxide (e.g., ZrOx),some other suitable dielectric, tantalum (e.g., Ta), tantalum nitride(e.g., TaN), titanium nitride (e.g., TiN), copper (e.g., Cu), cobalt(e.g., Co), ruthenium (e.g., Ru), molybdenum (e.g., Mo), iridium (e.g.,Ir), tungsten (e.g., W), or some other suitable metal.

FIGS. 7-22 illustrate cross-sectional views 700-2200 of some embodimentsof a method for forming an integrated chip comprising a first metal wire110 a and a second metal wire 110 b that are laterally separated by afirst cavity 114 a. Although FIGS. 7-22 are described in relation to amethod, it will be appreciated that the structures disclosed in FIGS.7-22 are not limited to such a method, but instead may stand alone asstructures independent of the method.

As shown in cross-sectional view 700 of FIG. 7 , a substrate 102 isprovided. Further, a plurality of semiconductor devices 104 are formedalong the substrate 102 and a first interconnect structure 106 is formedover the substrate 102.

The plurality of semiconductor devices 104 may, for example, be formedby any of an ion implantation process, a diffusion process, a depositionprocess, a photolithography process, or some other suitable process.

In some embodiments, the first interconnect structure 106 may compriseone or more lower etch-stop layers (e.g., 106 e of FIGS. 2 and/or 3 ),one or more lower dielectric layers (e.g., 106 d of FIGS. 2 and/or 3 ),one or more contacts (e.g., 106 c of FIGS. 2 and/or 3 ), one or morelower vias (e.g., 106 v of FIG. 3 ), one or more lower metal wires(e.g., 106 w of FIG. 3 ), or some other suitable features. In someembodiments, the first interconnect structure 106 may, for example, beformed by depositing the one or more lower etch-stop layers (e.g., 106 eof FIGS. 2 and/or 3 ) over the substrate 102, depositing the one or morelower dielectric layers (e.g., 106 d of FIGS. 2 and/or 3 ) over theetch-stop layer, patterning the one or more lower dielectric layers andthe one or more lower etch-stop layers to form one or more openings insaid layers, and forming the one or more contacts (e.g., 106 c of FIGS.2 and/or 3 ), the one or more lower vias (e.g., 106 v of FIG. 3 ),and/or the one or more lower metal wires (e.g., 106 w of FIG. 3 ) insaid openings.

As shown in cross-sectional view 800 of FIG. 8 , a first etch-stop layer108 is formed over the first interconnect structure 106 and a firstdielectric layer 802 is formed over the first etch-stop layer 108.

The first etch-stop layer 108 may, for example, be formed by depositingany of silicon carbide (e.g., SiC), silicon oxide (e.g., SiO2), siliconoxycarbide (e.g., SiOC), silicon nitride (e.g., SiN), siliconcarbonitride (e.g., SiCN), silicon oxynitride (e.g., SiON), siliconoxycarbonitride (e.g., SiOCN), aluminum oxynitride (e.g., AlON),aluminum oxide (e.g., AlO), or some other suitable dielectric over thesubstrate 102 by any of a physical vapor deposition (PVD) process, achemical vapor deposition (CVD) process, an atomic layer deposition(ALD) process, a spin-on process, or some other suitable process. Atemperature during the deposition may, for example, be about 150 to 400degrees Celsius or some other suitable value. A thickness of the firstetch-stop layer 108 may, for example, be about 10 to 1000 angstroms orsome other suitable value.

The first dielectric layer 802 may, for example, be formed by depositingany of silicon carbide, silicon oxide, silicon oxycarbide, siliconnitride, silicon carbonitride, silicon oxynitride, siliconoxycarbonitride, some other low-k dielectric (e.g., having a dielectricconstant of less than about 3.9), some other extreme low-k dielectric(e.g., having a dielectric constant of less than about 2), or some othersuitable dielectric over the substrate 102 by any of a PVD process, aCVD process, an ALD process, a spin on process, or some other suitableprocess. A temperature during the deposition may, for example, be about50 to 400 degrees Celsius or some other suitable value. A thickness ofthe first dielectric layer 802 may, for example, be about 30 to 800angstroms or some other suitable value.

As shown in cross-sectional view 900 of FIG. 9 , the first dielectriclayer 802 and the first etch-stop layer 108 are patterned to define aplurality of dielectric structures 904 from the first dielectric layer802. The patterning may, for example, comprise: 1) forming a mask 902over the first dielectric layer 802; 2) performing an etch into thefirst dielectric layer 802 and the first etch-stop layer 108 with themask in place; and 3) removing the mask 902. Other suitable patterningprocess(es) is/are however, amenable.

The mask 902 may, for example, comprise photoresist, silicon oxide,titanium nitride (e.g., TiN), or some other suitable material. The etchmay, for example, comprise a wet etching process, a dry etching process,or some other suitable etching process.

As shown in cross-sectional view 1000 of FIG. 10 , a metal layer 1002 isdeposited over the substrate 102 and between the plurality of dielectricstructures 904. The metal layer 1002 may, for example, comprise any oneor combination of tantalum (e.g., Ta), tantalum nitride (e.g., TaN),titanium nitride (e.g., TiN), copper (e.g., Cu), cobalt (e.g., Co),ruthenium (e.g., Ru), molybdenum (e.g., Mo), iridium (e.g., Jr),tungsten (e.g., W), or some other suitable material and may be depositedby any of a sputtering process, an electrochemical plating process, anelectroless deposition process, a PVD process, a CVD process, an ALDprocess, or some other suitable process. A temperature during thedeposition may, for example, be about 150 to 400 degrees Celsius or someother suitable value. A thickness of the metal layer 1002 may, forexample, be about 10 to 1000 angstroms or some other suitable value.

As shown in cross-sectional view 1100 of FIG. 11 , a planarizationprocess is performed on the metal layer 1002 to define a plurality ofmetal wires 110. For example, the planarization process defines a firstmetal wire 110 a and a second metal wire 110 b of the plurality of metalwires 110. The first metal wire 110 a and the second metal wire 110 bare laterally separated by a first dielectric structure 904 a of theplurality of dielectric structures 904 and by the first etch-stop layer108.

The planarization process may also be performed on the plurality ofdielectric structures 904. As a result, top surfaces of the plurality ofmetal wires 110 and top surfaces of the plurality of dielectricstructures 904 may be approximately coplanar. The planarization processmay, for example, be or comprise a chemical-mechanical planarization(CMP) or some other suitable planarization process.

Although FIGS. 8 to 11 illustrate the plurality of metal wires 110 asbeing formed by depositing the metal layer 1002 between the plurality ofdielectric structures 904 and subsequently planarizing the metal layer1002, it will be appreciated that in some alternative embodiments, themetal layer 1002 may be deposited over the first interconnect structure106, the metal layer 1002 may then be patterned to define the pluralityof metal wires 110, a dielectric layer may then be deposited over themetal wires 110 and between the metal wires to form the plurality ofdielectric structures 904, and the planarization process may then beperformed on the dielectric layer.

As shown in cross-sectional view 1200 of FIG. 12 , a capping layer 1202is deposited on top surfaces of the plurality of metal wires 110 to forma plurality of capping structures 1204 on the top surfaces of theplurality of metal wires 110. For example, a first capping structure1204 a is formed on a first top surface of the first metal wire 110 aand the second capping structure 1204 b is formed on a second topsurface of the second metal wire 110 b. The capping layer 1202 and hencethe plurality of capping structures 1204 may comprise one or moredielectrics, one or more metals, or some other suitable material.

In some embodiments, the capping layer 1202 is deposited over theplurality of metal wires 110 and over the plurality of dielectricstructures 904 by any of a CVD process, a PVD process, an ALD process, aspin on process, an electrochemical plating (ECP) process, a sputteringprocess, or some other suitable process. Further, in such embodiments,the capping layer 1202 is subsequently patterned to remove the cappinglayer 1202 from top surfaces of the plurality of dielectric structures904 and to define the plurality of capping structures 1204. In suchembodiments, the patterning may, for example, comprise aphotolithography/etching processor some other suitable patterningprocess. In some embodiments, a portion 1202 z of the capping layer 1202may remain on the first dielectric structure 904 a due to a misalignmentand/or offset when patterning the capping layer 1202.

In some other embodiments, the capping layer 1202 is selectivelydeposited so the capping layer 1202 deposits on the top surfaces of theplurality of metal wires 110 but not on top surfaces of the plurality ofdielectric structures 904. The selective deposition may, for example, beperformed by way of an area-selective ALD process or some other suitableselective deposition process. For example, the selective depositionprocess may comprise functionalizing top surfaces of the plurality ofdielectric structures 904 (e.g., forming self-assembled monolayers(SAMs) or some other functional layer(s) on top surfaces of theplurality of dielectric structures 904) and depositing the capping layer1202 by an ALD process. The functional layer(s) on the top surfaces ofthe plurality of dielectric structures 904 may block the capping layer1202 from being deposited on the top surfaces of the plurality ofdielectric structures 904.

In some embodiments, a small amount of the capping layer 1202 may beformed on the plurality of dielectric structures 904 during the ALDprocess. For example, the capping layer 1202 may be deposited on theplurality of dielectric structures 904 at a substantially slower ratethan on the plurality of metal wires 110. In such embodiments, an atomiclayer etching (ALE) process or some other suitable etching process maybe performed to remove the small amount of capping layer 1202 from theplurality of dielectric structures 904. In some embodiments, thefunctionalization process, the deposition process, and the etchingprocess may be repeated a number of times until the desired result isachieved. In some embodiments, a portion 1202 z of the capping layer1202 may be formed on the first dielectric structure 904 a due to a lossof selectivity when forming the capping layer 1202.

A temperature during the deposition may, for example, be about 20 to 400degrees Celsius (e.g., when the capping layer 1202 comprises a metal),about 150 to 400 degrees Celsius (e.g., when the capping layer 1202comprises a dielectric), or some other suitable value. Further, thecapping layer 1202 and hence the plurality of capping structures 1204may have a thickness of about 10 to 1000 angstroms or some othersuitable value.

The capping layer 1202 may, for example, comprise any of hafnium oxide(e.g., HfO), lithium niobium oxide (e.g., LiNbO), lithium nickel oxide(e.g., LiNiO), magnesium oxide (e.g., MgO), manganese oxide (e.g., MnO),molybdenum oxide (e.g., MoO), niobium oxide (e.g., NbO), nickel oxide(e.g., NiO), silicon oxide (e.g., SiO), silicon oxycarbide (e.g., SiOC),silicon oxycarbonitride (e.g., SiOCN), silicon oxynitride (e.g., SiON),silicon carbide (e.g., SiC), tin oxide (e.g., SnO), tin silicon oxide(e.g., SnSiO), strontium oxide (e.g., SrO), tantalum oxide (e.g., TaO),tantalum oxynitride (e.g., TaON), titanium oxide (e.g., TiO), titaniumoxynitride (e.g., TiON), tungsten oxide (e.g., WO), zinc oxide (e.g.,ZnO), zirconium oxide (e.g., ZrOx), some other suitable dielectric,tantalum (e.g., Ta), tantalum nitride (e.g., TaN), titanium nitride(e.g., TiN), copper (e.g., Cu), cobalt (e.g., Co), ruthenium (e.g., Ru),molybdenum (e.g., Mo), iridium (e.g., Ir), tungsten (e.g., W), or someother suitable metal.

As shown in cross-sectional view 1300 of FIG. 13 , the plurality ofdielectric structures 904 are removed from between the plurality ofmetal wires 110. For example, the first dielectric structure 904 a isremoved from between the first metal wire 110 a and the second metalwire 110 b.

In some embodiments, the plurality of dielectric structures 904 may beremoved by a dry etching process or some other suitable process. Forexample, the plurality of dielectric structures 904 may be removed by aninductively coupled plasma (ICP) or capacitively coupled plasma (CCP)reactive ion etching (RIE) process that may utilize any one orcombination of methane (e.g., CH4), fluoromethane (e.g., CH3F),difluoromethane (e.g., CH2F2), trifluoromethane (e.g., CHF3),octafluorocyclobutane (e.g., C4F8), hexafluoro-1,3-butadiene (e.g.,C4F6), tetrafluoromethane (e.g., CF4), hydrogen (e.g., H2), hydrogenbromide (e.g., HBr), carbon monoxide (e.g., CO), carbon dioxide (e.g.,CO2), oxygen (e.g., O2), boron trichloride (e.g., BCl3), chlorine (e.g.,C12), nitrogen (e.g., N2), helium (e.g., He), neon (e.g., Ne), argon(e.g., Ar), or some other suitable gas. In some embodiments, a pressureduring the etching may, for example, be about 0.2 to 120 millitorr orsome other suitable value. A temperature during the etching may, forexample, be about 0 to 100 degrees Celsius or some other suitable value.A power applied during the etching may be about 50 to 3000 watts or someother suitable value. A bias voltage applied during the etching may, forexample, be about 0 to 1200 volts or some other suitable value.

In some embodiments, the plurality of capping structures 1204 may act asa hard mask during the etching process. Further, the etching process maybe highly selective to the plurality of dielectric structures 904relative to the plurality of capping structures 1204 (e.g., theplurality of dielectric structures 904 may be etched at a substantiallyfaster rate than the plurality of capping structures 1204). For example,the etching process may remove the plurality of dielectric structures904 a first rate and may remove the plurality of capping structures 1204at a second rate that is slower than the first rate by a factor of about10 or more, by a factor of 20 or more, or by some other factor.

Because the plurality of dielectric structures 904 have a highselectivity relative to the plurality of capping structures 1204 duringthe etching process, top surfaces the plurality of metal wires 110 maynot be damaged during the etching process. For example, the plurality ofcapping structures 1204 may protect the top surfaces of the underlyingplurality of metal wires 110 from the etching process.

Further, because of the anisotropic characteristics of the dry etchingprocess used to remove the plurality of dielectric structures 904, theetching process may not etch away and/or damage sidewalls of theplurality of metal wires 110. For example, because the dry etchingprocess used has little to no lateral component, sidewalls of theplurality of metal wires 110 may not be damaged during the etching.

As a result, in some embodiments, top surfaces and sidewalls of theplurality of metal wires 110 may be substantially planar. Additionally,or alternatively, the top surfaces and sidewalls of the plurality ofmetal wires 110 may be devoid of nanoscopic voids. Thus, a structuralintegrity of the plurality of metal wires 110 may not be reduced and ahence a reliability of the plurality of metal wires 110 may be high.

In contrast, were the plurality of dielectric structures 904 to beremoved with an etch without the plurality of capping structures 1204 onthe top surfaces of the plurality of metal wires 110, the top surfacesof the plurality of metal wires 110 could be damaged by the etch.Sidewalls of the plurality of metal wires 110 could also be damaged bythe etch if the etch were performed without the plurality of cappingstructures 1204 in place.

FIGS. 14 to 19 illustrate cross-sectional views 1400-1900 of firstembodiments for performing a remainder of the method. The acts at FIGS.14 to 19 proceed from the acts at FIGS. 7-13 in the first embodiments ofthe method.

As shown in cross-sectional view 1400 of FIG. 14 , a sacrificial layer1402 is deposited over the substrate 102 and between the plurality ofmetal wires 110. The sacrificial layer 1402 may take the place of thepreviously removed plurality of dielectric structures (e.g., 904 of FIG.12 ). The sacrificial layer 1402 may, for example, comprise some organicmaterial (e.g., some carbon-based material) or some other suitablematerial and may be deposited by any of a PVD process, a CVD process, anALD process, a spin on process, or some other suitable process. Atemperature during the deposition may, for example, be about 50 to 400degrees Celsius or some other suitable value. The sacrificial layer 1402may, for example, have a thickness of about 30 to 600 angstroms or someother suitable value.

As shown in cross-sectional view 1500 of FIG. 15 , the sacrificial layer1402 is recessed to define a plurality of sacrificial structures 1502between the plurality of metal wires 110. As a result, top surfaces ofthe plurality of sacrificial structures 1502 are below top surfaces ofthe plurality of metal wires 110 (e.g., below the first top surface ofthe first metal wire 110 a and below the second top surface of thesecond metal wire 110 b). For example, the recessing defines a firstsacrificial structure 1502 a between the first metal wire 110 a and thesecond metal wire 110 b.

The recessing may, for example, comprise a dry etching process or someother suitable process. For example, recessing may comprise an ICP orCCP reactive ion etching (RIE) process that may utilize any one orcombination of methane, fluoromethane, difluoromethane,trifluoromethane, octafluorocyclobutane, hexafluoro-1,3-butadiene,tetrafluoromethane, hydrogen, hydrogen bromide, carbon monoxide, carbondioxide, oxygen, boron trichloride, chlorine, nitrogen, helium, neon,argon, or some other suitable gas. In some embodiments, a pressureduring the etching may, for example, be about 0.2 to 120 millitorr orsome other suitable value. A temperature during the etching may, forexample, be about 0 to 100 degrees Celsius or some other suitable value.A power applied during the etching may be about 50 to 3000 watts or someother suitable value. A bias voltage applied during the etching may, forexample, be about 0 to 1200 volts or some other suitable value.

In some embodiments, the recessing results in the plurality ofsacrificial structures 1502 having curved (e.g., concave) upper surfaces1502 u.

In some embodiments, the plurality of capping structures 1204 may act asa hard mask during the recessing process. Further, the recessing processmay be highly selective to the sacrificial layer 1402 relative to theplurality of capping structures 1204 (e.g., the sacrificial layer 1402may be etched at a substantially faster rate than the plurality ofcapping structures 1204).

Because the sacrificial layer 1402 has a high selectivity relative tothe plurality of capping structures 1204 during the recessing process,top surfaces the plurality of metal wires 110 may not be damaged duringthe recessing process. Further, because of the anisotropiccharacteristics of the dry etching process used to recess thesacrificial layer 1402, the recessing process may not etch away and/ordamage sidewalls of the plurality of metal wires 110.

As a result, in some embodiments, top surfaces and sidewalls of theplurality of metal wires 110 may remain substantially planar.Additionally, or alternatively, the top surfaces and sidewalls of theplurality of metal wires 110 may remain devoid of nanoscopic voids.Thus, a structural integrity of the plurality of metal wires 110 may bemaintained and a hence a reliability of the plurality of metal wires 110may be high.

As shown in cross-sectional view 1600 of FIG. 16 , a second dielectriclayer 1602 is formed directly over the plurality of sacrificialstructures 1502 and between the plurality of metal wires 110. The seconddielectric layer 1602 may, for example, be formed by depositing any ofsilicon carbide, silicon oxide, silicon oxycarbide, silicon nitride,silicon carbonitride, silicon oxynitride, silicon oxycarbonitride, someother low-k dielectric (e.g., having a dielectric constant of less thanabout 3.9), some other extreme low-k dielectric (e.g., having adielectric constant of less than about 2), or some other suitabledielectric over the substrate 102 by any of a PVD process, a CVDprocess, an ALD process, a spin on process, or some other suitableprocess. A temperature during the deposition may, for example, be about50 to 400 degrees Celsius or some other suitable value. A thickness ofthe second dielectric layer 1602 may, for example, be about 30 to 800angstroms or some other suitable value or some other suitable value.

As shown in cross-sectional view 1700 of FIG. 17 , the plurality ofsacrificial structures 1502 are removed from directly below the seconddielectric layer 1602 and from between the plurality of metal wires 110,thereby leaving a plurality of cavities 114 in place of the plurality ofsacrificial structures 1502. For example, the first sacrificialstructure 1502 a is removed from between the first metal wire 110 a andthe second metal wire 110 b, thereby leaving a first cavity 114 a inplace of the first sacrificial structure 1502 a.

The plurality of sacrificial structures 1502 are be removed fromdirectly below the second dielectric layer 1602 with the seconddielectric layer 1602 in place. In some embodiments, the plurality ofsacrificial structures 1502 may, for example, be removed by a thermal(e.g., baking) process which may vaporize the plurality of sacrificialstructures 1502 and the vapor may escape the plurality of cavities 114by passing through the second dielectric layer 1602. In some otherembodiments, the plurality of sacrificial structures 1502 may bevaporized upon being exposed to a laser or a UV light. In some otherembodiments, some other process(es) may be used to remove the pluralityof sacrificial structures 1502 from directly below the second dielectriclayer 1602.

In some embodiments, the plurality of sacrificial structures 1502 maynot be entirely removed from directly below the second dielectric layer1602 and from between the plurality of metal wires 110. As a result, aplurality of residual sacrificial structures (e.g., 302 of FIG. 3 ) mayremain directly below the second dielectric layer 1602 and between theplurality of metal wires 110.

As shown in cross-sectional view 1800 of FIG. 18 , a planarizationprocess is performed on the second dielectric layer 1602 to define aplurality of dielectric caps 112 and on the plurality of cappingstructures 1204 to remove the plurality of capping structures 1204 fromover the plurality of metal wires 110. For example, the planarizationprocess defines a first dielectric cap 112 a of the plurality ofdielectric caps 112 that is between the first metal wire and the secondmetal wire 110 b, and that is directly over the first cavity 114 a.

The planarization process may also be performed on the plurality ofmetal wires 110. As a result, top surfaces of the plurality of metalwires 110 and top surfaces of the plurality of dielectric caps 112 maybe approximately coplanar. For example, a top surface of the first metalwire, a top surface of the second metal wire 110 b, and a top surface ofthe first dielectric cap 112 a may be approximal coplanar. Theplanarization process may, for example, be or comprise a CMP or someother suitable planarization process.

Although FIGS. 16 to 18 illustrate the second dielectric layer 1602being planarized after the plurality of sacrificial structures 1502 areremoved, it will be appreciated that in some other embodiments, thesecond dielectric layer 1602 may be planarized before the plurality ofsacrificial structures (e.g., 1502 of FIGS. 15 and 16 ) are removed.

Further, in some embodiments, the planarization process may not entirelyremove the plurality of capping structures 1204 from over the pluralityof metal wires 110. Thus, in such embodiment's, a plurality of residualcapping structures (e.g., 502 of FIG. 5 ) may remain over the pluralityof metal wires 110.

As shown in cross-sectional view 1900 of FIG. 19 , a second interconnectstructure 116 is formed over the plurality of metal wires 110 and theplurality of dielectric caps 112. The second interconnect structure 116may, for example, be formed by repeating the aforementioned method toform one or more upper etch-stop layers (e.g., 116 e of FIG. 2 ), one ormore upper dielectric layers (e.g., 116 d of FIG. 2 ), one or more uppervias (e.g., 116 v of FIG. 2 ), one or more upper metal wires (e.g., 116w of FIG. 2 ), one or more upper cavities (e.g., 116 c of FIG. 2 ), orsome other suitable features.

For example, in some embodiments, an upper etch-stop layer (e.g., 116 eof FIGS. 2 and/or 3 ) may be formed over the plurality of metal wires110 and over the plurality of dielectric caps 112 by depositing any oneor more of silicon carbide, silicon oxide, silicon oxycarbide, siliconnitride, silicon carbonitride, silicon oxynitride, siliconoxycarbonitride, aluminum oxynitride, aluminum oxide, or some othersuitable dielectric over the substrate 102 by any of a CVD process, aPVD process, an ALD process, a spin on process, or some other suitableprocess. A temperature during the deposition may, for example, be about150 to 400 degrees Celsius or some other suitable value. A thickness ofthe upper etch-stop layer (e.g., 116 e of FIGS. 2 and/or 3 ) may, forexample, be about 10 to 1000 angstroms or some other suitable value.

FIGS. 20 to 22 illustrate cross-sectional views 2000-2200 of secondembodiments for performing the remainder of the method. The acts atFIGS. 20 to 22 proceed from the acts at FIGS. 7-13 , while skipping theacts at FIGS. 14-19 , in the second embodiments of the method.

As shown in cross-sectional view 2000 of FIG. 20 , a second dielectriclayer 2002 is formed directly over first etch-stop layer 108 and betweenthe plurality of metal wires 110. The second dielectric layer 2002 may,for example, be formed by depositing any of silicon carbide, siliconoxide, silicon oxycarbide, silicon nitride, silicon carbonitride,silicon oxynitride, silicon oxycarbonitride, some other low-k dielectric(e.g., having a dielectric constant of less than about 3.9), some otherextreme low-k dielectric (e.g., having a dielectric constant of lessthan about 2), or some other suitable dielectric over the substrate 102by any of a PVD process, a CVD process, an ALD process, a spin onprocess, or some other suitable process. A temperature during thedeposition may, for example, be about 50 to 400 degrees Celsius or someother suitable value. A thickness of the second dielectric layer 2002may, for example, be about 30 to 800 angstroms or some other suitablevalue.

A plurality of cavities 114 exist within the second dielectric layer2002 and between the plurality of metal wires 110 after depositing thesecond dielectric layer 2002. For example, a first cavity 114 a existsbetween the first metal wire 110 a and the second metal wire 110 b andis defined by one or more surfaces of the second dielectric layer 2002.The plurality of cavities 114 may exist because of the conformalityand/or fill capabilities of the deposition of the second dielectriclayer 2002. For example, a pitch of the plurality of metal wires 110 maybe small and hence the second dielectric layer 2002 may not completelyfill a space between the plurality of metal wires 110. As a result, theplurality of cavities 114 are formed within the second dielectric layer2002 between the plurality of metal wires 110.

As shown in cross-sectional view 2100 of FIG. 21 , a planarizationprocess is performed on the second dielectric layer 2002 to define aplurality of dielectric caps 112 and on the plurality of cappingstructures 1204 to remove the plurality of capping structures 1204 fromover the plurality of metal wires 110. For example, the planarizationprocess defines a first dielectric cap 112 a of the plurality ofdielectric caps 112.

The planarization process may also be performed on the plurality ofmetal wires 110. As a result, tops surfaces of the plurality of metalwires 110 and top surfaces of the plurality of dielectric caps 112 maybe approximately coplanar. For example, a top surface of the first metalwire, a top surface of the second metal wire 110 b, and a top surface ofthe first dielectric cap 112 a may be approximal coplanar. Theplanarization process may, for example, be or comprise a CMP or someother suitable planarization process.

Further, in some embodiments, the planarization process may not entirelyremove the plurality of capping structures 1204 from over the pluralityof metal wires 110. Thus, in such embodiment's, a plurality of residualcapping structures (e.g., 602 of FIG. 6 ) may remain over the pluralityof metal wires 110.

As shown in cross-sectional view 2200 of FIG. 22 , a second interconnectstructure 116 is formed over the plurality of metal wires 110 and theplurality of dielectric caps 112. The second interconnect structure 116may, for example, be formed by repeating the aforementioned method toform one or more upper etch-stop layers (e.g., 116 e of FIG. 6A), one ormore upper dielectric layers (e.g., 116 d of FIG. 6A), one or more uppervias (e.g., 116 v of FIG. 6A), one or more upper metal wires (e.g., 116w of FIG. 6A), one or more upper cavities (e.g., 116 c of FIG. 6A), orsome other suitable features.

For example, in some embodiments, an upper etch-stop layer (e.g., 116 eof FIG. 6A) may be formed over the plurality of metal wires 110 and overthe plurality of dielectric caps 112 by depositing any one or more ofsilicon carbide, silicon oxide, silicon oxycarbide, silicon nitride,silicon carbonitride, silicon oxynitride, silicon oxycarbonitride,aluminum oxynitride, aluminum oxide, or some other suitable dielectricover the substrate 102 by any of a CVD process, a PVD process, an ALDprocess, a spin on process, or some other suitable process. Atemperature during the deposition may, for example, be about 150 to 400degrees Celsius or some other suitable value. A thickness of the upperetch-stop layer (e.g., 116 e of FIG. 6A) may, for example, be about 10to 1000 angstroms or some other suitable value.

FIG. 23 illustrates a flow diagram of some embodiments of a method 2300for forming an integrated chip comprising a first metal wire and asecond metal wire that are laterally separated by a first cavity. Whilemethod 2300 is illustrated and described below as a series of acts orevents, it will be appreciated that the illustrated ordering of suchacts or events are not to be interpreted in a limiting sense. Forexample, some acts may occur in different orders and/or concurrentlywith other acts or events apart from those illustrated and/or describedherein. In addition, not all illustrated acts may be required toimplement one or more aspects or embodiments of the description herein.Further, one or more of the acts depicted herein may be carried out inone or more separate acts and/or phases.

At 2302, a first metal wire and a second metal wire are formed over asubstrate. The first and second metal wires are laterally separated by afirst dielectric layer and by an etch-stop layer. FIGS. 9 to 11illustrate cross-sectional views 900-1100 of some embodimentscorresponding to act 2302.

At 2304, a first capping layer is formed on a first top surface of thefirst metal wire and on a second top surface of the second metal wire toform a first capping structure and a second capping structurerespectively on the first and second top surfaces. FIG. 12 illustrates across-sectional view 1200 of some embodiments corresponding to act 2304.

At 2306, the first dielectric layer is removed from between the firstmetal wire and the second metal wire. FIG. 13 illustrates across-sectional view 1300 of some embodiments corresponding to act 2306.

Acts 2308 a, 2310 a, 2312 a, 2314 a, 2316 a, and 2318 a illustrate afirst embodiment for performing a remainder of the method 2300.

At 2308 a, a sacrificial layer is deposited over the etch-stop layer andbetween the first and second of metal wires. FIG. 14 illustrates across-sectional view 1400 of some embodiments corresponding to act 2308a.

At 2310 a, the sacrificial layer is recessed to define a firstsacrificial structure between the first and second metal wires. FIG. 15illustrates a cross-sectional view 1500 of some embodimentscorresponding to act 2310 a.

At 2312 a, a second dielectric layer is deposited directly over thefirst sacrificial structure and between the first and second metalwires. FIG. 16 illustrates a cross-sectional view 1600 of someembodiments corresponding to act 2312 a.

At 2314 a, the first sacrificial structure is removed from directlybelow the second dielectric layer and from between the first and secondmetal wires, thereby leaving a first cavity in place of the firstsacrificial structure. FIG. 17 illustrates a cross-sectional view 1700of some embodiments corresponding to act 2314 a.

At 2316 a, the second dielectric layer is planarized. FIG. 18illustrates a cross-sectional view 1800 of some embodimentscorresponding to act 2316 a.

At 2318 a, an interconnect structure is formed over the seconddielectric layer and over the first and second metal wires. FIG. 19illustrates a cross-sectional view 1900 of some embodimentscorresponding to act 2318 a.

Acts 2308 b, 2310 b, and 2312 b illustrate a second embodiment forperforming the remainder of the method 2300.

At 2308 b, a second dielectric layer is deposited over the etch-stoplayer and between the first and second metal wires such that a firstcavity exists within the second dielectric layer and between the firstand second metal wires after depositing the second dielectric layer.FIG. 20 illustrates a cross-sectional view 2000 of some embodimentscorresponding to act 2308 b.

At 2310 b, the second dielectric layer is planarized. FIG. 21illustrates a cross-sectional view 2100 of some embodimentscorresponding to act 2310 b.

At 2312 b, an interconnect structure is formed over the seconddielectric layer and over the first and second metal wires. FIG. 22illustrates a cross-sectional view 2200 of some embodimentscorresponding to act 2312 b.

Thus, the present disclosure relates to an integrated chip comprisingone or more cavities for improving a performance of the integrate chip,and a method of forming the integrated chip for improving a reliabilityof the integrated chip.

Accordingly, in some embodiments, the present disclosure relates to anintegrated chip comprising a substrate. A first conductive wire is overthe substrate. A second conductive wire is over the substrate and isadjacent to the first conductive wire. A first dielectric cap islaterally between the first conductive wire and the second conductivewire. The first dielectric cap laterally separates the first conductivewire from the second conductive wire. The first dielectric cap comprisesa first dielectric material. A first cavity is directly below the firstdielectric cap and is laterally between the first conductive wire andthe second conductive wire. The first cavity is defined by one or moresurfaces of the first dielectric cap.

In other embodiments, the present disclosure relates to an integratedchip comprising a substrate. A first metal wire is over the substrate. Asecond metal wire is over the substrate and is laterally adjacent to thefirst metal wire. An etch-stop layer is over the substrate and islaterally between a first sidewall of the first metal wire and a secondsidewall of the second metal wire. The etch-stop layer laterallyseparates the first sidewall from the second sidewall along bottoms ofthe first and second metal wires. A first dielectric cap is directlyover the etch-stop layer and is laterally between the first sidewall ofthe first metal wire and the second sidewall of the second metal wire.The first dielectric cap laterally separates the first metal wire fromthe second metal wire along tops of the first and second metal wires. Afirst cavity is directly below the first dielectric cap and is directlyover the etch-stop layer. The first cavity laterally separates the firstsidewall of the first metal wire from the second sidewall of the secondmetal wire. The first cavity comprises a first gas. The first cavity isdefined by one or more surfaces of the first dielectric cap. Further,the first sidewall of the first metal wire and the second sidewall ofthe second metal wire are devoid of nanoscopic voids.

In yet other embodiments, the present disclosure relates to a method forforming an integrated chip. The method comprises forming a first metalwire and a second metal wire over a substrate. The first metal wire andthe second metal wire are laterally separated by a first dielectricstructure. A capping layer is deposited on a first top surface of thefirst metal wire and a second top surface of the second metal wire at afaster rate than on a top surface of the first dielectric structure toform a first capping structure and a second capping structurerespectively on the first and second top surfaces. A first etch isperformed with the first capping structure and the second cappingstructure in place to remove the first dielectric structure from betweenthe first metal wire and the second metal wire. The first etch removesthe first dielectric structure at a faster rate than the first andsecond capping structures. A dielectric layer is formed between thefirst metal wire and the second metal wire. A first cavity is formedbetween the first and second metal wires after depositing the dielectriclayer. The first cavity is defined by one or more surfaces of thedielectric layer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for forming an integrated chip, themethod comprising: forming a first metal wire and a second metal wireover a substrate, wherein the first metal wire and the second metal wireare laterally separated by a first dielectric structure; depositing acapping layer on a first top surface of the first metal wire and asecond top surface of the second metal wire at a faster rate than on atop surface of the first dielectric structure to form a first cappingstructure and a second capping structure respectively on the first andsecond top surfaces; performing a first etch with the first cappingstructure and the second capping structure in place to remove the firstdielectric structure from between the first metal wire and the secondmetal wire, wherein the first etch removes the first dielectricstructure at a faster rate than the first and second capping structures;depositing a sacrificial layer over the first capping structure, overthe second capping structure, and between the first metal wire and thesecond metal wire after performing the first etch; recessing thesacrificial layer from over the first capping structure and the secondcapping structure to below the first capping structure, the secondcapping structure, the first top surface, and the second top surface toform a first sacrificial structure between the first metal wire and thesecond metal wire; depositing a dielectric layer between the first metalwire and the second metal wire and directly over the first sacrificialstructure after the recessing; and removing the first sacrificialstructure from directly below the dielectric layer and from between thefirst and second metal wires, thereby leaving a first cavity in place ofthe first sacrificial structure, wherein the first cavity is formedbetween the first and second metal wires, and wherein the first cavityis defined by one or more surfaces of the dielectric layer.
 2. Themethod of claim 1, wherein the first etch removes the first dielectricstructure at a first rate and removes the first and second cappingstructures at a second rate, and wherein the first rate is greater thanthe second rate by a factor of 10 or more.
 3. The method of claim 1,further comprising: performing a planarization process on the dielectriclayer, the first capping structure, and the second capping structure toremove the dielectric layer, the first capping structure, and the secondcapping structure from over the first metal wire and the second metalwire, wherein the dielectric layer is directly over the first cavity anddirectly between the first metal wire and the second metal wire afterthe planarization process is performed.
 4. The method of claim 1,wherein the capping layer comprises a metal, and wherein the metal isselectively deposited on the first top surface of the first metal wireand on the second top surface of the second metal wire such that the topsurface of the first dielectric structure is devoid of the metal afterthe capping layer is deposited.
 5. The method of claim 1, wherein thefirst capping structure and the second capping structure remain over thefirst metal wire and the second metal wire, respectively, after thefirst etch.
 6. The method of claim 1, wherein the first cappingstructure extends along the first top surface from a first sidewall ofthe first metal wire to a second sidewall of the first metal wire,wherein the second capping structure extends along the second topsurface from a first sidewall of the second metal wire to a secondsidewall of the second metal wire, wherein the first capping structureand the second capping structure are laterally spaced apart with a spacetherebetween before the first etch is performed, and wherein the spaceis delimited by a sidewall of the first capping structure, a sidewall ofthe second capping structure, and the top surface of the firstdielectric structure.
 7. The method of claim 1, wherein a pair ofsidewalls of the first capping structure are directly over the firstmetal wire and extend from a top surface of the first capping structureto the first top surface of the first metal wire before the first etchis performed, and wherein a pair of sidewalls of the second cappingstructure are directly over the second metal wire and extend from a topsurface of the second capping structure to the second top surface of thesecond metal wire before the first etch is performed.
 8. The method ofclaim 1, wherein a sidewall of the second capping structure is directlyover the first dielectric structure and extends from a top surface ofthe second capping structure to a top surface of the first dielectricstructure.
 9. The method of claim 8, wherein a portion of the firstdielectric structure remains along a sidewall of the second metal wireafter the first etch is performed.
 10. The method of claim 9, whereinthe dielectric layer is formed along a sidewall of the portion of thefirst dielectric structure after the first etch is performed, whereinthe portion of the first dielectric structure is directly between thedielectric layer and the second metal wire, and wherein the portion ofthe first dielectric structure further defines the first cavity.
 11. Amethod for forming an integrated chip, the method comprising: forming afirst metal wire and a second metal wire laterally spaced apart over asubstrate, wherein a first dielectric layer is directly between thefirst metal wire and the second metal wire; forming a first cappingstructure over the first metal wire and a second capping structure overthe second metal wire, wherein the first capping structure and thesecond capping structure are laterally spaced apart, wherein the firstdielectric layer is between the first capping structure and the secondcapping structure, and wherein a sidewall of the second cappingstructure is directly over the first dielectric layer and extends from atop surface of the second capping structure to a top surface of thefirst dielectric layer; removing the first dielectric layer fromdirectly between the first metal wire and the second metal wire with thefirst capping structure and the second capping structure in place overthe first metal wire and the second metal wire, respectively, wherein aportion of the first dielectric layer remains along a sidewall of thesecond metal wire after the removing; depositing a second dielectriclayer between the first metal wire and the second metal wire, wherein afirst cavity is formed between the first metal wire and the second metalwire; and removing the first capping structure and the second cappingstructure from over the first metal wire and the second metal wire afterthe depositing of the second dielectric layer.
 12. The method of claim11, wherein forming the first capping structure and the second cappingstructure comprises selectively depositing a capping layer over thefirst metal wire and the second metal wire.
 13. The method of claim 12,wherein the capping layer is deposited on the first metal wire and thesecond metal wire at a first rate, wherein the capping layer isdeposited on the first dielectric layer at a second rate, and whereinthe first rate is greater than the second rate.
 14. The method of claim12, wherein the selectively depositing the capping layer over the firstmetal wire and the second metal wire comprises forming a blocking layeron a top surface of the first dielectric layer and depositing thecapping layer with the blocking layer in place.
 15. The method of claim11, wherein removing the first dielectric layer from directly betweenthe first metal wire and the second metal wire comprises etching thefirst dielectric layer, wherein the etching removes the first dielectriclayer at a first rate, wherein the etching removes the first cappingstructure and the second capping structure at a second rate, and whereinthe first rate is greater than the second rate.
 16. The method of claim11, further comprising: depositing a sacrificial layer over the firstcapping structure, over the second capping structure, and directlybetween the first metal wire and the second metal wire; recessing thesacrificial layer from over the first capping structure and the secondcapping structure to below a top surface of the first capping structure,a top surface of the second capping structure, a top surface of thefirst metal wire, and a top surface of the second metal wire with thefirst and second capping structures in place to form a sacrificialstructure between the first metal wire and the second metal wire,wherein the second dielectric layer is deposited over the sacrificialstructure and between the first metal wire and the second metal wire;and removing the sacrificial structure from between the first metal wireand the second metal wire and from under the second dielectric layer toform the first cavity between the first metal wire and the second metalwire and under the second dielectric layer, wherein a lower surface ofthe second dielectric layer delimits a top of the first cavity, andwherein the lower surface extends from a sidewall of the first metalwire to a sidewall of the portion of the first dielectric layer.
 17. Themethod of claim 11, wherein the portion of the first dielectric layercovers the sidewall of the second metal wire, wherein the seconddielectric layer is deposited directly between the first metal wire andthe portion of the first dielectric layer, and wherein the portion ofthe first dielectric layer partially delimits the first cavity.
 18. Amethod for forming an integrated chip, the method comprising: forming afirst metal wire and a second metal wire over a substrate, wherein thefirst metal wire and the second metal wire are laterally spaced apart,and wherein a first dielectric layer is directly between the first metalwire and the second metal wire; selectively depositing a capping layerover the first metal wire and the second metal wire so that a topsurface of the first metal wire and a top surface of the second metalwire are covered by the capping layer and a top surface of the firstdielectric layer is uncovered, wherein the first dielectric layer isbetween a first sidewall of the capping layer and a second sidewall ofthe capping layer; etching the uncovered top surface of the firstdielectric layer with the capping layer in place to remove the firstdielectric layer from between the first metal wire and the second metalwire; depositing a sacrificial layer over the capping layer and directlybetween the first metal wire and the second metal wire; recessing thesacrificial layer from over the capping layer to below the cappinglayer, below the top surface of the first metal wire, and below the topsurface of the second metal wire to form a recessed sacrificial layerbetween the first metal wire and the second metal wire; depositing asecond dielectric layer between the first metal wire and the secondmetal wire and over the recessed sacrificial layer; and removing therecessed sacrificial layer from between the first metal wire and thesecond metal wire and from under the second dielectric layer to form acavity between the first metal wire and the second metal wire, whereinthe cavity is delimited by a surface of the second dielectric layer. 19.The method of claim 18, wherein a portion of the recessed sacrificiallayer remains between the first metal wire and the second metal wireafter the removing of the recessed sacrificial layer, and wherein theportion of the recessed sacrificial layer further delimits the cavity.20. The method of claim 19, wherein the portion of the recessedsacrificial layer comprises carbon and extends along a sidewall of thefirst metal wire and a sidewall of the second metal wire, and whereinthe second dielectric layer is on the portion of the recessedsacrificial layer.